Thermal structures of accreting neutron stars with neutrino losses due to strong pion condensations

TL;DR

This paper models the thermal structures of accreting neutron stars considering neutrino losses from strong pion condensations, explaining observed quiescent X-ray luminosities without invoking direct Urca processes.

Contribution

It introduces a new explanation for quiescent X-ray luminosities based on pion condensation neutrino emission, challenging previous models requiring nucleon or hyperon Urca processes.

Findings

Neutrino emission from strong pion condensation can account for observed luminosities.

The model matches observed data for SAX J1808.4-3658.

Alternative Urca processes are not necessary in this context.

Abstract

Quiescent X-ray luminosities are presented in low mass X-ray binaries with use of evolutionary calculations. The calculated luminosities are compared with observed ones in terms of timeaveraged mass accretion rate. It is shown that neutrino emission by strong pion condensation can explain quiescent X-ray luminosity of SAX J1808.4-3658 and we do not need direct Urca processes concerning nucleons and/or hyperons.